Workers in painting, automobile, textile, printing, and pharmaceutical industries are exposed to vapors from organic solvents that are recognized by National Institute of Occupational Safety and Hygiene (NIOSH) as carcinogens, reproductive hazards, and/or neurotoxins. Workers in these industries wear Air Purifier Respirators (APRs) equipped with respirator cartridges on their faces to protect themselves from breathing such vapors. Specifically, activated carbon that is packed within each respirator cartridge adsorbs organic vapors to prevent them from reaching the workers'breathing zone. To minimize the risk of exceeding the adsorption capacity of the carbon, which would result in breakthrough and inhalation of organic vapors, NIOSH has recommended the use of end-of-service life indicators (ESLI) in APRs. Although ESLIs have been developed for some toxic gases (e.g., ammonia), there are no commercial ESLIs available for organic vapors such as toluene. In the absence of ESLIs for organic vapors, NIOSH requires manufacturers to develop (and users to adopt) complex cartridge- changing schedules that are cumbersome to implement, prone to error, and complicated by factors such as fluctuations in temperature and humidity, breathing rate of the user, and the concentration of the vapors. To address the unmet need for an ESLI for organic vapors that can be integrated into APRs and thereby meet the NIOSH recommendations and reduce the health risks associated with exposure to organic vapors, this proposal seeks to initiate the development of a fundamentally new liquid crystal (LC)-based technology for reporting organic vapors in ESLIs. The motivation for the development of the new technology is two-fold: First, the high cost, requirement for power, and large foot print does not allow the sensors based on existing or emerging technologies for detection of volatile organic compounds (VOC) to be integrated as ESLIs for respirator cartridges. Second, the ambiguities associated with colorimetric readout technologies do not meet NIOSH standards for ESLI applications. This proposal seeks to initiate the development of a technology that has the potential to create a passive and inexpensive ESLI that can be integrated into respirator cartridges for toluene. Because the LC-based technology offers a passive platform for gas detection, it can be fabricated as a simple, cartridge-mountable format that will overcome the barriers that have prevented adoption of existing sensing technologies as ESLIs for organic vapors. PUBLIC HEALTH RELEVANCE: Workers in multiple industries are exposed to vapors from organic solvents that are health hazards (carcinogens, reproductive hazards, and/or neurotoxins). In the absence of technologies suitable for use as end-of-service-life-indicators (ESLI) for organic vapors in respirators cartridges, manufacturers have developed (and workers are required to follow) complex, cost ineffective, and ambiguous cartridge- changing schedules to replace the respirator cartridges before they no longer protect the users. This proposal seeks to initiate the development of a liquid crystal-based technology that has the potential to create a passive and inexpensive ESLI sensor that can be integrated into respirator cartridges for toluene. Because the LC-based technology offers a passive platform for gas detection, it can be fabricated as a simple, cartridge-mountable format that will overcome the barriers that have prevented adoption of existing sensing technologies as ESLIs for organic vapors.